Photo-on-Demand Phosgenation Reactions That Cross Three Phases of a Heterogeneous Solution of Chloroform and Aqueous NaOH.

Here, we report a novel photo-on-demand phosgenation reaction that crosses three phases of a heterogeneous solution of chloroform (CHCl) and aqueous NaOH containing an aryl alcohol or amine. This reaction system enables the safe, convenient, and inexpensive synthesis of carbonate esters, polycarbonates, and N-substituted ureas from aryl alcohols, aryl diols, and primary/secondary amines, respectively, on a practical scale and with good yield. The photochemical oxidation of CHCl to phosgene (COCl) occurs upon irradiation with UV light from a low-pressure mercury lamp of both the gas and liquid phases of the reaction system under O bubbling of the vigorously stirred sample solution. The following reaction mechanisms are suggested: The aryl alcohol reacts with the generated COCl at the interfaces of the organic/aqueous phases and aqueous/gas phases, in competition with the decomposition of COCl due to hydrolysis. Nucleophilicity and hydrophilicity are enhanced by the formation of aryl alkoxide ion through the reaction with NaOH, whereas the reaction of amine proceeds through neutralization of the generated HCl by the aqueous NaOH.